Extreme pressure steel mill lithium base grease containing sulfurized sperm oil and lead naphthenate



United States Patent EXTREME PRESSURE STEEL MILL LITHIUM BASE GREASE CONTAINING SULFURIZED SPERM OIL AND LEAD NAPHTHENATE Terence B. Jordan and John P. Dilworth, Fishkill, N.Y., assignors to Texaco Inc., a corporation of Delaware No Drawing. Filed Dec. 22, 1958, Ser. No. 781,901

9 Claims. (Cl. 252-36) This invention relates to a lithium soap grease possessing properties required for a grease used in steel mill lubrication. More particularly, this invention involves the discovery that production of a lithium soap grease meeting therigid specifications of a steel mill grease requires the use of a very specific mixture of additives.

This application is a continuation-in-part of our copending applications Serial No. 482,670 filed January 18, 1955, now abandoned, and Serial No. 702,517 filed December 13, 1957.

Lithium base greases have met with wide acceptance as general purpose greases. They are water-resistant, have high dropping points in the neighborhood of 340 to 400 F. and provide lubrication over a wide temperature range. The instant invention discloses how EP properties are imparted to lithium base greases without impairing the other properties so that they qualify for heavy duty use in steel mill lubrication.

Prior to this invention, steel mill greases were formulated by the incorporation of halogenated aromatics such as dichlorodiphenyl and tetrachloronaphthalene in calcium base greases. These greases, while they meet the rigorous high dropping point and extreme pressure specifications required for steel mill lubrication, had the serious drawback of high toxicity. The instant invention provides a steel mill grease which has the required high temperature and EP properties for steel mill grease without the drawback of possessing high toxicity.

The steel mill greases of this invention comprise an oleaginous lubricating base as the major component, lithium soap of a hydroxy stearic acid in a concentration which is determined by the grade of grease desired, 4 to 15 percent sulfurized sperm oil and 1 to 5 percent of a lead salt of a low molecular weight naphthenic acid. The grease of the invention advantageously contains 0.3 to 0.8 percent glycerine which is incorporated per se or in the form of the glyceride of l2-hydroxy stearic acid, hydrogenated castor oil. One of the important features of this invention is the discovery of the necessity of employing a lead soap of naphthenic acid having an average molecular weight below 235 in order to produce a grease having the desired EP properties. If the EP' additive com bination comprises the common lead naphthenate which is formed from a naphthenic acid having an average molecular weight about 300 in combination with sulfurized sperm oil, a decidedly inferior product from the standpoint of EP properties and yield is obtained. Conventional antioxidants such as diphenylamine and phenyl alpha-naphthylamine are usually incorporated in the grease.

The requirements for a multi-purpose grease for use in steel mills have been largely dictated by the major users of these products. The requirements set up by the large users of steel mill greases are particularly stringent with respect to dropping point, shear stability, oxidation and water resistance, load carrying capacity and corrosion characteristics. In addition there are certain flash, pour and viscosity requirements on the mineral oil component; of these greases. The base oil requirements will be discussed liereafter. The more important requirements of the finished grease are shown in Table I, which is a consolidated specification for. a multi-purpose steel mill grease.

3,003,962 Patented Oct. 10, 1961 ice TABLE I Characteristic Consolidated Specification Dropping Point 350 F., Min. Shear Stability:

Worked 10,000 Strokes 10% change, rnax. Shell Roller Test- Increase in Penetration; 50 points, max. Decrease in Penetration 10% max. Bomb Oxidation at 210 F., p.s.i. drop in 10 max. rs. Load Carrying Capacity:

Timken, OK Load, lb 45 min. Shell Four-Ball Machine, 3-hr.-Weld kg. min. Corrosion, 50 hr. at F.:

Copper. No blackening. Steel D0. Water Resistance 14-L-5 (MO-150 F.) Grease Loss, 2.5 max.

Percent.

ized sperm oil and a lead salt of a naphthenic acid having an average molecular weight below 235 in a grease containing as the soap base a lithium hydroxy stearate.

The soap component of the steel mill greases of the invention is a lithium salt of l2-hydroxy stearic acid. In the manufacture of the steel mill greases of the invention, 12-hydroxy stearic acid per se, a monoester thereof such as methyl 12-hydroxy stearate, its glyceride, hydrogenated castor oil or mixtures thereof, may be employed. In the manufacture of the No. 0 grade grease, however, it is necessary to add 0.3 to 0.8 weight percent glycerine per se or in the form of hydrogenated castor oil in order to meet the dropping point requirements as disclosed in the afore-identified application Serial No. 702,517. As a matter of convenience, the desired glycerine content is normally supplied by using hydrogenated castor oil as the soap precursor. Since hydrogenated castor oil is generally used for the manufacture of No. 0 grade grease having the required minimum dropping point of 350 F., it is the preferred soap precursor for the manufacture of the steel mill greases of the invention.

As pointed out in the afore-identified copending application Serial No. 702,517, now abandoned, the excellent grease yield obtained with the EP additive of this invention, namely sulfurized sperm oil and a lead salt of a naphthenic acid having an average molecular weight below about 235, has the effect that a product meeting No. 0 grade penetration requirements is formed with such a low soap content that the product does not consistently meet the 350 F. minimum dropping point requirement,

improved EP properties. The presence of the prescribed amount of glycerine permits a substantial reduction of the concentration of the BP additive mixture of sulfurized sperm oil and low molecular weight lead naphthenate.

The soap concentration of .the greases of this inven tion range from about 4.5 to 15.0 weight percent. Since.

cost is a factor in large volume products such as this, the

soap content is as low as possible while permitting the. attainment of the minimum 350 F. dropping point requir'ement'as outlined above. One of the features of this invention is that the additive mixture of sulfurized sperm oil and lead soap of naphthenic acids "having an average I molecular weight below about 235 substantially improves the grease yield as will be shown hereafter.

The glycerine concentration prescribed for improving the EP properties and depressing the grease yield so that the No. grade grease product contains sufficient thickener to meet the minimum dropping point requirement is 0.3-0.8 weight percent. The preferred glycerine content is between 0.4 and 0.7 weight percent.

The lithium base greases of this invention are prepared by any standard procedure employed for lithium base greases. Either the so-called high-heat procedure or the so-called low-temperature method may be used with the former being preferred. The high-heat procedure involves saponification at a temperature in the range of 180 to 220 F. and dehydration at a temperature above the melting point of the soap base followed by controlled cooling with agitation through the transition temperature range. The high-heat procedure will be illustrated in more detail in the examples illustrating the invention. The low-temperature procedure is more particularly described in US. 2,450,219 and 2,450,220.

The additive combination, namely sulfurized sperm oil plus the lead salt of a naphthenic acid having an average molecular weight below 235, which enables the lithium 12- hydroxy stearate grease of the invention to meet the load carrying requirements without sacrificing shear stability, is incorporated in the lithium l2-hydroxy stearic grease mixture after the dehydrated grease has reached a temperature of about 200 F. Usually it is added with stirring at a temperature between 200 and 160 F.

Sulfurized sperm oil is a well-known EP agent and oxidation inhibitor which is widely used in the formation of gear lubricants. Sulfurized sperm oil is more technically described as sulfurized cetyl oleate. The sulfurized sperm oil usually comprises 4 to 15 percent of the total grease composition with the usual concentration being between 5 and 12 weight percent.

Lead naphthenate is also a well-known component of lubricants in which EP properties are required. The lead naphthenates usually employed as EP agents in lubricant compositions are formed from acids having an average molecular weight between 250 and 335 and are usual y isolated from heavy gas oil fractions. When high molecular weight lead naphthenates are used in combination with sulfurized sperm oil in a lithium hydroxy stearate grease, the resulting product does not meet the extreme pressure requirements of a steel mill grease as will be demonstrated hereafter. In contrast, a similar grease composition, with the exception that the lead naphthenate was formed from a naphthenic acid having a molecular weight below 235, meets these specifications.

The average molecular weight of the naphthenic acid from which the lead salt is prepared should be between 120 and 235, and preferably between 200 and 230. This requirement eliminates tricyclic naphthenic acids and limits the usable material to monoor di-cyclic naphthenic acids. An outstanding steel mill grease is obtained by using a lead salt of a naphthenic acid having an average molecular weight of about 223.

The low molecular weight lead naphthenate constitutes 1 to 5 weight percent of the grease composition with l to 3 weight percent normally being used.

The requirements of the lubricating base component of a steel mill grease are a flash, COC, of 375 F. minimum, an SSU viscosity at 210 F. of 75 minimum, and a pour of 40 F. maximum. A mineral oil or synthetic lubricating base meeting these requirements can be used. Since these requirements are easily met with a hydrocarbon base oil, the lubricating base usually comprises a hydrocarbon base oil rather than the more expensive synthetic lubricating bases. However, if a synthetic lubricating base is used, it can be an aliphatic diester of a dicarboxylic acid or an aliphatic diester of a dihydroxy alcohol, a polyalkylene ether, a silicone or a tetraalkyl silicate. Since these materials are all well known in the art and are only rarely used in the greases of this invention, they will not be further described.

A distillate oil, a residuum, or a mixture thereof can be used as the lubricating base as long as the require ments of 375 F. minimum flash point, a +40 F. maximum pour point and an SSU viscosity at 210 F. of 75 minimum are met. Since cost is an important factor in the large volume products such as steel mill grease, a residual oil advantageously constitutes a large portion of the lubricating base. A preferred mixture comprises 20% of a refined distillate oil having an SUS viscosity at F. of to and at 210 F. of 44 minimum, and 80 percent of a refined residuum having a flash of 470 and an SUS viscosity at 210 F. of 102 to 110. Both the distillate oil and residuum were refined by a procedure involving furfural refining, acid treating, clay contacting and solvent dewaxing. The mixture of 20 percent distillate oil and 80 percent refined residuum had the following properties: a flash of 440 F. minimum, an SUS viscosity at 210 F. between 80 and 84, a VI above 76 and a pour of 5 F. maximum. In the subsequent description of the invention, this mixture of distillate oil and residuum was used.

The following examples illustrate the production of the steel mill greases of the invention and the eifectiveness of the sulfurized sperm oil-low molecular weight lead naphthenate EP additive mixture in improving the yield and EP properties of lithium hydroxy stearate greases. Example 1 shows the production of a No. 1 NLGI grade grease using the EP additive mixture of the invention. Example 2 demonstrates that an additive mixture of sulfurized sperm oil and the lead salt of a high molecular weight naphthenic acid gives a smaller yield of a product having poorer EP properties than the product obtained in Example 1.

Example 1 To a fire-heated kettle, there were charged methyl l2-hydroxy stearate, lithium hydroxide, mineral oil (approximately of the total mineral oil used in the grease formulation) and water. The mineral oil comprised the previously described mixture of 20% of a refined paraifin base distillate oil and 80% of a refined residual. The mixture was saponified at 200-220 F. for a period of 1.5 hrs. and was subsequently dehydrated by heating to a temperature of 290310 F. After the dehydration step, which took approximately 0.75 hr., the remainder of the mineral oil was added and the resulting mixture heated to 400 F. The heat was then shut off to the kettle and the grease mixture circulated through a Chatfee disperser and concentric tube cooler unit until a temperature of 200 F. was reached. At this point, sulfurized sperm oil and lead naphthenate derived from an acid having an average molecular weight of 223 and diphenylamine were added in amounts to give the following composition on a weight basis:

The properties of this product are shown in Table 11.

Example 2 Another grease was prepared by the high temperature procedure outlined in Example 1. The grease prepared in this example was'essentially the same as the grease prepared in Example 1 with the distinction that the lead naphthenate employed in conjunction with sulfurized sperm oil was derived from a naphthenic acid having an average molecular weight of about 322. The resulting grease had the following composition on a weight basis:

The properties of this product are also shown on Table II in comparison with the grease composition of Example l.

TABLE II Tests Examplel Example 2 NLGI Grade 1 ASTM Penetration:

Change, Percent 3 Shell Roller Test: Penetration Change, Percent 2 Dropping Point, F... 369 367 Timken Tester0 K-l 45 30 Shell Four-Ball Machi load, before welding, kg ASTM Bomb Oxidation-Drop at 100 hrs.,

p.s.1. Water Leaching Test, Percent Loss Water Washing and Busting Test:

Grease on Bearing, Percent 60 us None Corrosion at 160 F.:

Copper Negative Steel- Negative Pumpability b I 2 O gJmin. Free Flow 6 Heat Stability, 96 hrs. at 250 1 1.2,

Unworked Penetration Change, Percent Worked Penetration Change, Percent.

A comparison of the greases prepared in Examples 1 and 2 show the following important facts with regard to the critical nature of the prescribed sulfurized sperm oil-low molecular weight. lead naphthenate EP additive mixture in the steel mill greases of the invention;

Even though the soap content of the grease prepared in Example 2 is higher than the soap content of Example 1, namely 5.25 weight percent vs. 5.1 weight percent, the Example 2 product is a No. 0 gradegrease whereas the Example 1 product is a No. 1- grade grease. This proves that higher yields are obtained with the additive mixture of sulfurized sperm oil-low molecular weight lead naphthenate than with an additive mixture in which a high molecular weight lead naphthenate is used in conjunction with sulfurized sperm oil.

The second significant fact is that the load-carrying capacity of the grease of Example 2 is definitely inferior to the load-carrying capacity of the grease of Example 1. In the Timken OK Test, a value of 30 lbs. was obtained with the Example 2 product whereas a Timken OK value of 45 lbs. Was obtained with the Example 1 product. Since the Example 2 grease failed to meet the Timken OK Test load-carrying requirement of steel mill users as set forth in Table I, no further tests were made thereon.

The Example 1 product met all the requirements of an NLGI No. 1 steel mill grease and has met with wide acceptance in steel mill use.

Examples 3 to 5 demonstrate the necessity of adding glycerine in the maufacture of a No. 0 grade grease. Example 3 shows the difliculty of meeting dropping point specifications using methyl l2-hydroxy stearate as the soap precursor because of the high yield resulting from the use of an EP additive mixture of sulfurized sperm oil and a low molecular weight lead naphthenate. Example 4 shows that the substitution of hydrogenated castor oil for methyl l2-hydroxy stearate decreases the yield of the lithium hydroxy stearate grease, assures the attainment of the 350 F. minimum dropping poinL-and increasesgthe EPpmperties of the resulting grease compostion; Example 5 shows that the action of the glycerine derived from hydrogenated castor oil in improving the EP properties of the grease permits a'substantial decrease in the concentration of the EP additive mixtureof sulfurized sperm oil and low molecular weight lead naphthenate. This reduction in concentration of the EP additive mixture significantly reduces the cost of .the No. 0 grade grease even though the yield is depressed.

Example 3 V To a fire-heated kettle there were charged 25 lbs. of methyl 12-hydroxy stearate, 0.25 lb. of lithium hydroxide, 2.18 lbs. of water, and 15 lbs. of mineral oil which is approximately /3 ofthe total mineral oil used in the grease formulation. The mineral oil comprises 20 percent of a refined paraflin base distillate-and percent of a refined residuum as previously described. The reaction mixture was saponified at 200-220 F. for a period. of 1.5 hours and subsequently dehydrated by heating to a temperature of 290310 F". After dehydration, which took approximately v7.5 hours, the remainder ofithe' mineral oil was added and the resulting mixture heated to 400 F- The heating of the kettle was. then stopped and the grease mixture was circulated'through a Chaifee disperser and a concentric tube cooler until a temperature of 200 F. was reached. At this point, 6.5 lbs. of sulfurized sperm oil, 1.3 lbs. of lead naphthenate formed from a naphthenic acid having an average molecular weight of 223 and 0.35 lbs. of diphenylamine were add-.

ed. The grease was drawn at 172 F. The composi-. tions and properties of this grease are shown in Table In i I Example 4 ,A No. 0 grade lithium hydroxy stearate grease .was prepared by a procedure similar to that outlined in-Example 3' with the;exceptionthat hydrogenated castorv oil wasemployed as the soap precursor in place of methyl l2-hydroxy stearate. The composition and properties of the resulting grease are also shown in Table HI. I I

Another grease composition was prepared employing hy-' drogenated castor oil as thesoap precursor and employing a substantially smaller concentration of the EP- additive mixture of sulfurized sperm oil and lead naphthenate wasprepared by the procedure outlined in Example 3. The composition and properties of this grease fcomposition are shown in Table III.

TABLE III Example 3 Example 4 Example 5 (Methyl Composition l2-hydroxy stearate) (Hydrogenated Castor Oil) Lithium lz-hydroxy stearate wt. percent-. 3. 7 5.0 6.0 Glycerine d0 0. 5 0. 6 Mineral 011.... do 83.7 81. 8 84. 8 Excess LiOH -410. 0. 1 0. 2 0. 1 sulfurized sperm oil do 10. 1 10.1 6.7 Lead naphthenate. do 1. 9 1. 9 1. 3 Diphenylamine do 0. 5 0. 5 0. 5 Properties:

NLGI Grade 0 0 O ASIM Penetration at 77 F.

Unworked 400 341 355 Worked 357 379 370 Dropping Point, F 852 856 362 Timken Test, lbs. OK 45 50 60 The data an Table III demonstrate that the use of hythough the grease prepared in Example 3 using methyl IZ-hydroxy stearate as the soap precursor had a dropping point of 352 F., this value was so close to the minimum 350 F. requirement that plant production of the No. grade grease with methyl 12-hydroxy stearate or 12hydroxy stearic acid as a soap precursor consistently failed to meet this requirement.

The failure of plant production to produce a No. 0 grade grease meeting the 350 F. minimum dropping point requirement employing methyl 12-hydroxy stearate as the soap precursor is illustrated by the following representative data:

In one instance, a plant batch was prepared in accordance with the procedure outlined in Example 3 and employing methyl 12-hydroxy stearate as the soap precursor; the concentrations of extreme pressure additives and excess lithium hydroxide were the same as in Example 3. The resulting product, which had a lithium IZ-hydroxy stearate soap content of 3.8 weight percent had a worked penetration of 374 and a dropping point of 336 F. A second plant batch having a lithium soap content of 3.9 weight percent had a worked penetration of 364 and a dropping point of 328 F.

In contrast with the failure of plant produced No. 0 grade greases prepared from methyl 12-hydroxy stearate to meet the minimum dropping point of 350 F., plant production of No. 0 grade greases empolying hydrogenated castor oil as the soap precursor has consistently met and surpassed the 350 F. dropping point requirement.

It is also significant that the grease of Example 4 employing the hydrogenated castor oil as the soap precursor had a significantly higher Timken value than the grease in Example 3 although both contained the same concentration of additive mixture of sulfurized sperm oil and lead naphthenate, namely, 12 weight percent.

As shown in Example 5, the use of hydrogenated castor oil and the resulting presence of glycerine in a grease permits approximately a 30 percent reduction in the concentration of the EP additive mixture while actually raising the Timken OK Test of the resulting grease. The improved Timken 0K test obtained in Example 5 over Example 4 is believed to be due primarily to a higher concentration of glycerine in Example 5.

Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

l. A grease adapted for steel mill lubrication and characterized by high dropping point and EP properties comprising a lubricating oil as the major component, 4.5 to 15.0 weight percent lithium IZ-hydroxy stearate as a thickening agent, 5-15 weight percent sulfurized sperm oil and 1 to 5 weight percent of a 'lead salt of a naphthenic acid having an average molecular weight between and 235.

2. A grease according to claim 1 containing 0.3 to 0.8 weight percent glycerine.

3. A grease according to claim 1 in which said lubricating oil comprises a mixture of refined distillate and residual oils.

4. A grease according to claim 1 containing 4 to 15 weight percent lithium 12-hydroxy stearate, 1 to 5 weight percent lead salt and 5 to 12 weight percent sulfurized sperm oil.

5. A grease according to claim 1 in which hydrogenated castor oil is used as the precursor of said lithium l2-hydroxy stearate.

6. A grease adapted for steel mill lubrication and characterized by high dropping point and EP properties comprising a mineral lubricating oil as a major component, 4.5 to 15.0 weight percent lithium 12-hydroxy stearate, 0.3 to 0.8 weight percent glycerine, 5 to 12. weight percent sulfurized sperm oil, 1 to 3 weight percent lead salt of a naphthenic acid having an average molecular weight between 120 and 235 and 0.1 weight percent excess lithium hydroxide.

7. A grease according to claim 6 in which said glycerine is incorporated by employing hydrogenated castor oil as the soap precursor.

8. A grease according to claim 6 in which said lead naphthenate is derived from a naphthenic acid having an average molecular Weight of about 223.

9. A grease according to claim 6 in which said mineral oil comprises a mixture of refined distillate and residual oils.

References Cited in the file of this patent UNITED STATES PATENTS 2,379,245 Morway et al June 26, 1945 2,652,366 Jones et al. Sept. 15, 1953 2,701,237 Sokol Feb. 1, 1955 OTHER REFERENCES Manufacture and Application of Lubricating Greases, Boner-Reinhold Pub. Corp., N.Y., 1954, pages 114 and 443, 143-145.

Ind. and Eng. Chem, vol. 33, pp. 1352-9, November, 1941. 

1. A GREASE ADAPTED FOR STEEL MILL LUBRICATION AND CHARACTERIZED BY HIGH DROPPING POINT AND EP PROPERTIES COMPRISING A LUBRICATING OIL AS THE MAJOR COMPONENT, 4.5 TO 15.0 WEIGHT PERCENT LITHIUM 12-HYDROXY STEARATE AS A THICKENING AGENT, 5-15 WEIGHT PERCENT SULFURIZED SPERM OIL AND 1 TO 5 WEIGHT PERCENT OF A LEAD SALT OF A NAPHTHENIC ACID HAVING AN AVERAGE MOLECULAR WEIGHT BETWEEN 120 AND
 235. 